The enzymatic system involved in dinitrogen fixation is being investigated at the molecular level to determine how the components of the nitrogenase system function in the process. Particular emphasis is being placed on the role of magnesium adenosine triphosphate in the process by which electrons are transferred from reduced ferredoxin through the iron protein of nitrogenase to the molybdenum iron protein and to dinitrogen. Experiments are in progress to determine whether the energy released by adenosine triphosphate hydrolysis during electron transfer is reflected in a lowering of the midpoint potential of the fully reduced state of the molybdenum-iron protein. The mechanism of control of the biosynthesis and functioning of nitrogenase is being investigated. Particularly how adenosine diphosphate and carbamyl phosphate bind to and inhibit the functioning of the nitrogenase system, will be pursued. In addition the role of iron and molybdenum in the catalytic function is being investigated.